/**
* Process a single block using the basic RSA algorithm.
*
* @param inBuf the input array.
* @param inOff the offset into the input buffer where the data starts.
* @param inLen the length of the data to be processed.
* @return the result of the RSA process.
* @exception DataLengthException the input block is too large.
*/
public virtual byte[] ProcessBlock(
byte[] inBuf,
int inOff,
int inLen)
{
if (core == null)
{
throw new InvalidOperationException("RSA engine not initialised");
}
return(core.ConvertOutput(core.ProcessBlock(core.ConvertInput(inBuf, inOff, inLen))));
}
/**
* Process a single block using the basic RSA algorithm.
*
* @param inBuf the input array.
* @param inOff the offset into the input buffer where the data starts.
* @param inLen the length of the data to be processed.
* @return the result of the RSA process.
* @exception DataLengthException the input block is too large.
*/
public virtual byte[] ProcessBlock(
byte[] inBuf,
int inOff,
int inLen)
{
if (key == null)
{
throw new InvalidOperationException("RSA engine not initialised");
}
BigInteger input = core.ConvertInput(inBuf, inOff, inLen);
BigInteger result;
if (key is RsaPrivateCrtKeyParameters)
{
RsaPrivateCrtKeyParameters k = (RsaPrivateCrtKeyParameters)key;
BigInteger e = k.PublicExponent;
if (e != null) // can't do blinding without a public exponent
{
BigInteger m = k.Modulus;
BigInteger r = BigIntegers.CreateRandomInRange(
BigInteger.One, m.Subtract(BigInteger.One), random);
BigInteger blindedInput = r.ModPow(e, m).Multiply(input).Mod(m);
BigInteger blindedResult = core.ProcessBlock(blindedInput);
BigInteger rInv = r.ModInverse(m);
result = blindedResult.Multiply(rInv).Mod(m);
// defence against Arjen Lenstra’s CRT attack
if (!input.Equals(result.ModPow(e, m)))
{
throw new InvalidOperationException("RSA engine faulty decryption/signing detected");
}
}
else
{
result = core.ProcessBlock(input);
}
}
else
{
result = core.ProcessBlock(input);
}
return(core.ConvertOutput(result));
}
/**
* Process a single block using the RSA blinding algorithm.
*
* @param in the input array.
* @param inOff the offset into the input buffer where the data starts.
* @param inLen the length of the data to be processed.
* @return the result of the RSA process.
* @throws DataLengthException the input block is too large.
*/
public virtual byte[] ProcessBlock(
byte[] inBuf,
int inOff,
int inLen)
{
BigInteger msg = core.ConvertInput(inBuf, inOff, inLen);
if (forEncryption)
{
msg = BlindMessage(msg);
}
else
{
msg = UnblindMessage(msg);
}
return(core.ConvertOutput(msg));
}